1. Field of the Invention
The present invention relates to flexible insulating cover structures, and, more particularly, to a detachable insulating cover assembly which is particularly suited for use in connection with greenhouses and similar applications, where large surface areas of a structure have to be covered with removable low cost insulating members.
2. Description of the Prior Art
It is known from the prior art that the heat loss through the walls of greenhouses and other heated structures can be greatly reduced through the use of inexpensive insulating cover members of plastic sheet material which are attached to the surfaces of the greenhouse. Comparative measurements have shown that energy savings of up to forty percent are achievable. Particularly advantageous for this purpose are plastic sheets which consist of two layers with small air cushions enclosed between them, so-called bubble sheets.
In one known application, large members of bubble sheet plastic have simply been bolted to the surfaces of a greenhouse, using screws and nuts with hold-down washers (described in the periodical "Zierpflanzenbau", Issue No. 9, Apr. 28, 1976, pp. 315-318).
In another known installation of this type, the plastic sheet cover members are attached to the greenhouse structure by means of special attachment fasteners which consist of a flat fastener base which is attached to a fastener stem whose rear extremity forms a ring. A fastener cap matching the fastener base is engageable over a forwardly extending portion of the fastener stem so as to firmly clamp the sheet between the base and cap, after it has been pierced by the extremity of the fastener stem. Once assembled, this fastener cannot be opened by hand. When the fastener members are pried apart with a tool, they are frequently unsuitable for reuse. These fastener assemblies are used in conjunction with attachment cables, a row of spaced fasteners being arranged near the edge of the plastic cover member, so as to either hang the cover member by one of its edges, or to stretch the cover member between parallel edges, when two or more spaced attachment cables are used. (Such an arrangement is described in a publication by BASF: "Kunststoffe in der Anwendung"--Werkstoffblatt 7013.1.02, October 1974, page 3.).